The cranium of a human infant is made up of frontal, parietal, temporal, occipital and other smaller bones that are separated by membranous intervals until brain growth is complete at eighteen to twenty-four months of age. Normally, the infant cranium is symmetrical in shape. However, in the condition known as plagiocephaly, the head is non-symmetrical, becoming parallelogram or rhomboid in shape. Sometimes the plagiocephalic head may correct its shape over time, but often the condition may persist, leading to facial asymmetry with functional, cosmetic, and other disabilities. If orthotic treatment is indicated, it is important to attempt correction of the deformation when the subject is less than a year old, before the sutures in the cranium have solidified.
The shape of the infant cranium is determined by multiple factors including brain growth and development, constraints placed on the skull during and after gestation, and bony abnormalities of the skull. When an infant's head is maintained in a nearly fixed position either in utero or when sleeping on a flat surface, the cranium may be progressively deformed. Thus, a condition known as occipital positional plagiocephaly or deformational plagiocephaly frequently occurs in children who sleep in a relatively constant position on their backs. For example, as a result of the American College of Pediatrics recommendation that children be placed on their back instead of on their stomach to avoid SIDS (Sudden Infant Death Syndrome), a significant number of new cranial deformities are being seen (Argenta, L. C., et al., J. Craniofac. Surg. 7:5-11 (1996)). In addition, many infants have craniums that are deformed either in utero or during the birth process, and sleeping on the depressed portion of the skull accentuates the deformity. Infants who are slower to develop motor activity may also develop cranial abnormalities because of their failure to move their heads frequently. Also, in some cases plagiocephaly is secondary to synostosis, a condition in which some of the skull sutures fuse too soon resulting in the skull bulging somewhere else as the brain grows.
Unfortunately, surgery is often the treatment prescribed to correct plagiocephaly of the infant skull. While plagiocephaly secondary to synostosis usually requires surgery, many deformities of the skull can be corrected with appropriate molding helmets (Argenta, L. C., et al., J. Craniofac. Surg. 7:5-11 (1996); Claren, S. K., et al., J. Pediatrics 94:43-46 (1979)). Such helmets take advantage of the pliability of the infant skull to mold the skull into a normal shape (see e.g., U.S. Pat. Nos. 4,776,324, 5,308,312, and 5,094,229). Still, these molding helmets can be constricting and uncomfortable for a small infant to wear. Also, such helmets are expensive to make and thus, are not accessible to the majority of patient who require treatment.
Thus, there is a need to develop corrective infant headgear that is comfortable for the infant to wear, and provides a gentle but effective therapy for the large majority of plagiocephalic infants. Rather than squeezing unaffected regions of the infant brain, it would be preferable to relieve the pressure from depressed areas of the skull, and thereby allow the skull to reform into its natural shape. To enable correction of the abnormality before the brain plates begin to fuse, the headgear must be comfortable enough to be worn for extended periods of time by the infant. In addition, therapeutic headgear for infants should be affordable and accessible to the many patients who require treatment.